If you take the trouble to read the Youtube TOS (http://www.youtube.com/static?gl=US&template=terms), especially point 5B, you'll see that downloading isn't allowed.
That's why I'm locking this thread.
i am using the YouTube Downloader HD and cannot download most of music videos and it always shows that this videos cannot be downloaded. can you please tell which type of free YouTube downloader which can be downloaded any type or any kind of version of YouTube music videos from YouTube ? highly appreciated and obliged if any good suggestions in this connection. thank you .... sara